You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <allfileusages gafcontinue="IMT_Faithful.png|179" />
  </query-continue>
  <query>
    <pages>
      <page pageid="10" ns="4" title="Infinitywiki:Community Portal" />
      <page pageid="53" ns="0" title="Marvel vs. Capcom: Eternity of Heroes" />
      <page pageid="54" ns="0" title="Super Marvel vs. Capcom: Eternity of Heroes" />
      <page pageid="163" ns="0" title="Content Architect" />
      <page pageid="170" ns="0" title="Contributors" />
      <page pageid="177" ns="0" title="Elecbyte" />
      <page pageid="183" ns="0" title="Infinity Artist" />
      <page pageid="581" ns="0" title="X-Men: Second Coming" />
      <page pageid="1025" ns="0" title="Get Hit" />
      <page pageid="1062" ns="0" title="Avengers vs. X-Men" />
    </pages>
  </query>
</api>